Multiple spindle honing machine



D. K. GIREENEENG MULTIPLE SPINDLE HONING MACHINE l- Sheeus-Sheet 1LFiled July 20, 1954 D. 1K. GREENBERG. VWM

MULTIPLE SPINDLE HONING MACHINE Aug., l

Filed July 20, 1954 4 Sheets-Sheet 2 @Lg 2u lili Aw@ I K. GREENBIEHGMULTIPLE SPINDLE HONING MACHINE Filed July 20, 1954 4 Sheets-Sheet 3 wwwAmig, x

D. K. GREENERG MULTIPLE SPINDLE HONING MACHINE Filed July 20, 19544Sheets-Sheet 4 @Enf 2,757,488 MULTIPLE SPINDLE HoNING MACHINE Donald K.Greenberg, Rockford, Ill., assigner to Barnes Drill Co., Rockford, Ill.,a corporation of Illinois Application July 20, 195.4, SerialNo. 444,483s claims. (ci. sla- 34) This invention relates to honing machines of themultiple spindle type for honing a plurality of parallel cylinderssimultaneously during relative reciprocation between the workpiece and asingle head carrying all of the honing tools. The invention has moreparticular reference to multiple honing machines in which the collapseof each hone is eitected individually and automatically under thecontrol of a sizing device which responds to changes in the size of thecylinder being honed and controls the expanding mechanism of the hone torelease the pressure on the stones and permit collapse of the hones whena predetermined size has been obtained.

ln certain honing operations, it is desirable after the work surface hasattained a certain size predetermined by an associated size measuringdevice to continue the reciprocation ot the rotating honing tool for afew strokes while the abrasive elements thereof are pressed against thework surface. Usually such supplemental honing or so-called sparking outis performed under lesser pressure than that used during the primaryhoning.

The primary object of the invention is to provide a multiple spindlehoning machine having a novel mechanism for controlling the supplementalhoning by the several hones to avoid any possibility of leaving thenished surfaces marred.

A further object is to effect the supplemental honing by the severalhones through a single timing control mechanism, thus minimizing thecost and complexity of the controls.

The invention also resides in the novel manner of utilizing the sizingsignals in controlling the reexpansion of the hones to effect thesupplemental honing while at the same time insuring that all of theditferent bores will be finished to precisely the same size.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings, in which Figure l is a fragmentary frontelevational view of a four spindle honing machine adapted to becontrolled in accordance with the present invention.

Fig. 2 is a schematic view of the main actuators and their controls.

Fig. 3 is a wiring diagram of the controls for one of the tool units.

Fig. 4 is a wiring diagram of the interrelated controls for all of thespindles.

The improved supplemental honing control is shown in the drawings in afour spindle production type machine having four tools 1t), 102, 10b,10c rotatable about parallel axes laterally spaced for the simultaneoushoning of bores 11, 11a, 11b, 11c in a workpiece 12 while the latter issupported in a suitable xture. The hones are carried by the lower endsof jointed Shanks 13 coupled to spindles 14 journaled on and projectingfrom a hollow head 15 which is slidable back and fourth on guide rods 16rigid with the machine frame. A motor 17 (Fig. 2) mounted 2,757,488Patented Aug. 7, 1956 on the frame drives the respective spindlesthrough separategear connections. Raising and lowering of the head 15 toenter `the collapsedhones `into or remove the same from the work boresand to reciprocate the expanded bones within the bores may be effectedby a hydraulic `actuator 19 mounted on the machine frame and suppliedwith pressure Huid from a motor driven `pump 20 under the control of areversing valve 21. Actuation of the latter is controlled by a pilotvalve 62 whose actuating rod 63 is urged by a spring 64 toward theposition shown in Fig. 2 to move `the tool head downwardly. Reversal ofthe valve position may be eected 'by energization of a solenoid or by acam 66 on an arm 67 loose on the shaft of a cam dial 6 8 which through aconnection 69 with the hone actuator 19 `is oscillated back and forthwith the up and down movements of the tool head 15.

Each honing tool comprises a series of stones 22 angularly spaced arounda body 23 and normally held as by the usual garter springs againstconical cams 24. The latter are fast on a rod 25 which extends upwardlythrough the hollow tool shank and spindle 12. When the rod is moveddownwardly, the stones 22 are expanded against the wall of the bore, theoutward pressure on the stones being continued while the spindle isrotated and reciprocated to enlarge the bore to the desired size.

Reciprocation of the rods 25 to expand and allow contraction of thehones may be effected by various types of power actuators, the one shownhere for purposes of illustration being of the type forming the subjectmatter of Seborg et al. application Serial No. 340,232, filed March 4,1953, to which reference may be made for further details. Each actuatorindicated generally at 27 is mounted on the tool head 15 and comprisestwo electric motors 28 and 29 respectively coupled through appropriategearing with the terminal elements 30 and 31 of a diierential gear 33herein of the planetary type. The spider or intermediate member 34carrying the planet gears is coupled through speed reduction gearingincluding a worm 37 to a nut 32 journaled on the head 15 and threadedonto a screw 36 on the expander rod.

It will be apparent that the rotary motions of the motors 28 and 29 arecombined by the differential 33 and, after a further speed reduction,are converted into reciprocatory motion of the expander rod 25. The gearratios are such that when both of the motors are operating in adirection to move the rod downwardly, the diameter of the hone 1t) willbe increased at a comparatively rapid rate, for example, .05 of an inchper second. On the other hand, when the motor 29 alone is operating. thediameter of the hone will be increased at a much slower rate, forexample, .0092 of an inch per second. This `slow rate is variable bymanually adjusting the knob 38 (Eig. 3) of a speed regulator 39.

Rapid contraction of the hone will occur when the fast motor 28 isoperating in the opposite direction either alone or with the motor `29thus raising the expanding rod 25. As will appear later, the maximumextent of such collapse of each hone is limited by opening of a switch1S by movement to the position shown in Fig. 2 of a rack bar 60 meshingwith a pinion 61 which in turn meshes with rack teeth on the upper endot the screw 36. Each of the switches 1S is associated with a switch 2Swhich is open when the associated hone is fully collapsed but closed atall other times. Quick stopping of the sun gear 39 abruptly when themotor 2S is deenergized is effected by a magnetically applied brake 40coupled to the motor shaft and connected in the motor circuit so as tobe released whenever the motor is energized.

Means is providedr `for signaling the engagement of the honing stoneswith the bore wall during the rapid expansion of the hone and. thereuponinterrupting the circuit for the winding of the higher speed poweractuator, the slower speed actuator continuing to operate to expand thestones during actual honing of the bore. Herein, this signaling meansincludes a switch 3S (Fig. 2) actuated by a device which is yieldable inresponse to the building up of a predetermined torque in the driveconnection to the hone expanding cams. The yielding device shownincludes the worm 37 (Fig. 2) whose supporting shaft 42 is urged againsta stop 43 by a spring 44. When the torque being transmitted to the wormwheel exceeds a comparatively low value, the spring 44 yields andpermits the Worm to shift axially whereupon a cam 45 actuates thefollower pin of the switch 3S, the latter controlling the stopping ofthe motor 28 and the application of the brake 40 as will appear later.

Associated with each hone is a device 50 for feeling of the bore as itis being enlarged, sensing the attainment of the desired size and, inresponse to such signal, initiating release of the expanding pressure orcollapse of the hone to discontinue its abrading action. The sizemeasuring device herein shown forms the subject matter of an applicationof James B. Klein, Serial No. 325,257, tiled December 11, 1952. Itcomprises a plug or gage ring 51 on the lower end of a sleeve 52surrounding the tool shank 13 and mounted on a bracket 53 (Fig. l) forlimited free oating laterally of the tool axis, and urged downwardly bya spring 54. Each of the rings is beveled at its lower end and sized toenter the bore when the latter has been enlarged to the proper size.

Through rods 55 having stops 56 thereon and slidable in ears 57 on thehead 15, the bracket 53 is suspended from the head so as to move withthe head during most of its down stroke and after the hones have enteredthe bores, the beveled ends of the plugs then coming against andbecoming seated in the upper ends of the bore walls. After the sleevethus stops in feeling engagement with the bore, the tool head and thehones continue on to the end of the downstroke, the ears 57 sliding downalong the rods 55 in this rst part of the downstroke of the heads. Inthis position of the plug, an arm 58 (Fig. 2) on the sleeve is stoppedshort of contact with the actuating pin of a switch 59 stationarilymounted on the fixture snpporting the workpiece.

When, by the action of the hone, any one of the bores has been enlargedto a diameter corresponding to the size of the plug 51, the latter willenter the end of the bore in the latter part of the downstroke of thetool head. The arm 58 thus moves far enough to engage and actuate theswitch 59 whose closure signals the attainment of the desired bore size.It will be observed that each of the sizing devices 50 operatesindependently of the others and feels of its bore during each downstroke of the tool head but fails to enter the bore until the latter hasbeen enlarged to the desired diameter.

In the honing of a multiple bore workpiece with a machine of the abovecharacter, the reciprocation of the tool head is continued until all ofthe hones have completed their respective bores, each hone being co1-lapsed when its bore comes up to size as determined by its associatedsizing device 50. The present invention contemplates a novelinterrelation of the controls for the several hone expanders 27 toprovide for substantially equalized supplemental honing or sparking outof all of the bores, preferably under light pressure in spite of thecompletion of the primary honing of the several bores at different timesfor any one workpiece and in diierent sequences in successiveworkpieces.

Generally stated, the improved control provides for collapsing each honewhen its work bore comes up to size and maintaining each hone collapseduntil all have completed the primary honing of the respective bores,then expanding all of the hones in response to the signal from thesizing device of the last bore to be nished, the sup-` plemental honingby all of the tools then continuing for the required short interval soas to leave all of the bores with a ne linish and unmarked in any way.After the supplemental honing has continued for a measured interval, allof the hones are collapsed and withdrawn simultaneously from the boresby upward movement of the tool head.

The desired light pressure of the honing stones against the bore wallsduring the supplemental honing is achieved by effecting this expansiononly by the motor 28 whose stopping is controlled by the torqueresponsive switch 3S. All of the hones may thus be brought into contactwith the bore walls under light pressure determined by the adjustment ofthe torque sensing device. Preferably, provision is made for onlypartially collapsing each hone in response to the signal from itsassociated sizing device 50.

Typical circuitry for controlling the execution of a cycle of the abovecharacter is shown in Figs, 3 and 4, the former showing the completecircuit for one honing tool with the addition of certain relays andswitches which are duplicated for the several tools and respectivelyindicated by postscripts a, b, and c. For example, the collapseindicating switches of the four tools are 2S, 28a, 2Sb, and 2SCrespectively. Also, the switches actuated by any relay are indicated bythe same reference character with the addition of numerical postscripts,1R1 and 1K2 being switches of the relay 1R. The rectangles shown in Fig.4 represent those parts of Fig. 3 which are duplicated for the differenttools. The time delay relays SR and 11R are of various well knownconstructions and adapted, when energized, to measure an adjustable timeinterval and then actuate associated switches, the relay being resetautomatically when deenergized.

Let it be assumed that the parts are positioned as shown in Figs, 2, 3,and 4 with all relays and solenoids deenergized, the tool head 15 fullyretracted upwardly, and all of the hones collapsed, this latt-ercondition being evidenced by closure of the switches 1S, 15a, 1Sb, and1Sc in the fully retracted position of the expander rods 25, 25a, 25h,and 25C.

To start the next cycle after a new workpiece has been fastened in thefixture, the start button 70 is depressed to energize a relay 1R throughthe then closed switch 2R1. The resulting closure of the switch 1R1energizes the relay 3R through switches 70, 1R1, 1S, 18a, lSb, and 1Scthereby energizing a relay 3R which closes its switch SR2 to reverse avalve 72 and direct pressure iluid through the pilot valve to the rightend of the reversing valve 21. The latter is shifted to admit pressureiluid to the upper end of the actuator 19 and thus initiate downwardmovement of the tool head 15. ln the initial clockwise turning of thedial 68 at the start of this movement, a dog 73 allows a switch 4S toclose thus completing circuits through switches 1K2, 1K3, and SR1 formaintaining the relays 1R and 3R energized independently of the startswitch and also of the 1S switches when the latter are opened later asthe hones are expanded.

In'the downward movement of the tool head, the hones enter the workbores but remain collapsed until at the extreme end of the stroke a dog75 on the dial 68 closes a switch 5S later to be described and alsoengages and shifts the arm 67 clockwise into engagement with a switch 6Swhich then remains closed during reciprocation of the tools back andforth in the work bore even though the arm 67 is oscillated back andforth by dogs 75 and 76. ln each clockwise movement of the arm, the cam66 rocks a lever 77 to reverse the position of the pilot valve 62 andthus cause the valve 21 to reverse the connection and initiate upwardmovement of the tool head by the actuator 19. As the dial and the dog 76swing the arm counterclockwise at the upper end of the working stroke,the cam 66 permitsr the spring 64 to shift the valve 62 back to theposition shown in Fig. 2 thus starting the next downstroke. Suchreciprocation of the tools back and forth continues until the end of thecycle and after all of the bores are up to size and the supplementalhoning has been completed as described later.

Closure of the switch GS as above described at the lower end of thefirst downstroke completes a circuit for energizing a relay 4R throughswitches TR1, 1K2, and 4S closing switches R1 and 4K2. Through parallelconductors 79, 79a, 79h, and 79C (Fig. 4), closure of the switch 4R31prepares the size measuring circuits later to be described whichcircuits include the switches 59, 59a, 5'9", and 59C of the respectivesizing devices Sil. Through conductors 78, 78a, 7h11, and 73 circuitsare completed by the switch LMR2 through then closed switches SR1, SRM,SRlb, and SRlic in the different expander units. The resultingenergization of relays 6R of these units closes a multiple switch tit)thereof to start the associated motor 28. This relay in each unit alsocloses a switch 6K1 to complete a circuit for the relay "IR through athen closed switch 5RS. Upon being energized, the relay IR becomessealed by its switch 'Rl and by closure of its switches 7K2, the feedmotor Z9 of the unit is started.

By the combined action of the two motors 2,8 and 29 of each expandingunit, each hone is expanded rapidly thus opening the associated switch1S and closing the companion switch 2S. When the stones of each honecome against the wall of its bore, the expander rod is blocked and theresulting torque build up in the drive connection causes the Worm toshift axially against the action of the spring 43 until the switch 3S isopened thereby deenergizing the relay 6R to deenergize the fast motor 28and apply its brake 4t). The motor 29 continues to run by virtue ofsealing the relay IR through switches 7K1, SR1, and 2S thus continuingthe expansion of the hone but at the slow rate to produce the heavystone pressure desired for the primary honing of the bore. All of thehones are thus expanded and remove stock from their respective bores asthey are reciproeated up and down in unison in the manner describedabove. In the latter part of each downstrolre of the tool head, the gagerings of the different units come into feeling engagement with the endsof the bores and failure of the rings to enter the bore causes theexpansion of the hones to continue in the further reciprocation of thetool head.

Assume now that the bore lll is the iirst to be finished as evidenced byentry of the gage ring Fill and closure of the switch 59. This completescircuits for energizing a signal light 81 to indicate that the bore l1is finished and also for two parallel relays 5R and lR which are sealedthrough the switches 5R2 and 4S. The relay til?. is of the time delaytype having a normally closed switch SR1 which, after energization ofthe relay is opened after the lapse of a predetermined interval longenough only to permit partial collapse of the hone by its motor Openingof the switch 5R1 by the relay 5R interrupts the sealing circuit of therelay '7K whose deenergization stops the slow motor 29 and the honeexpansion. At the same time, the closure of the switch SRS completes acircuit through the then closed timer switch SRl and the switch 2S toenergize a relay QR which closes switches F12-to start the motor 28 in adirection to collapse the hone. Energization of this relay also opensthe switch @Rl later used in preventing energization of the relay 6R.Another switch 5K4 is also closed by the relay 5R.

The collapse of the hone following termination of the primary honingneed only be sufficient to relieve the stresses in the expandingmechanism and therefore the heavy pressure of the stones against thework. Thus, the interval measured by the time delay relay SR is veryshort so that the hone is collapsed only partialy but sutiiciently todisengage the stones from the walls. The collapse is terminated when therelay SR opens its switch SR1 thus deenergizing the relay 9R to open theswitch 82.. As before, the motor 23 is stopped abruptly by its brake.

The same functions are performed by the expanding mechanisms of theother three hones 10a, 10b, and 10 in response to the sizing signal orclosure of the respective switches 59a, 59h, and 59. Thus, each hone ispartially collapsed as its bore cornes up to size thus interrupting theabrading action of that hone even though other of the hones may continuewith the primary honing of their bores. Each collapsed hone merelyreciprocates idly in its bore with the stones out of active contact withthe bore wall.

Finally, when the relays 5R of all four of the hones have becomeenergized and irrespective of the order of such energization, the fourswitches 5R41, 5R4a, b, and c will be closed and closure of the last oneof these completes a circuit including the switch 4S for energizing tworelays 10R and 11R, the latter being a time delay relay. When the relay10R closes the switches 10R1, lllRla, 10R1b, and 10R1c, circuits arecompleted for energizing the respective relays 6R in the case of thosehones which are already partially collapsed, these being the first threeof the hones to have completed the primary honing of their bores. Theresulting closure of the corresponding switches thus starts thecorresponding motors 28 to initiate reexpansion of these three hones. Inthe case of the last hone to complete its primary honing, suchreexpansion is delayed momentarily in order to insure that this honewill also be collapsed partially and the pressure of its stones on thebore Wall definitely relieved. Such delay is achieved by the action ofthe switch 9R1 in holding the energizing circuit for the relay 6R of thefourth hone open until this hone has been partially collapsed, theswitch 9Rl having been opened by the relay 9R when the latter initiatedthe collapsing operation of the motor 28 in response to energization ofthe relay 5R by the up-tosize signal by the last sizing device 50 toclose its switch 59.

Now when the last hone to linish its primary honing does becomepartially collapsed as evidenced by opening of the switch SR1 by thetime delay relay SR, the relay 9R will be deenergized and the switch 9R1closed to permit energization of the relay 6R and closure of theswitches 80 of this unit to initiate reexpansion of the fourth hone.There is therefore a delay between the start of the reexpansion forsupplemental honing between the first three of the hones to nish theirprimary honing and the fourth or last hone to finish such honing. Thetime difference is so short however as to have no eifect on theuniformity in the sizes of the nal bores particularly in view of thelight pressure to which the work is subjected during the supplementalhoning which pressure is produced by the motors 29 and is limited by theadjustment of the torque responsive switches 3S.

The invention contemplates again using the mechanism that terminates therapid expansion for the primary honing to interrupt the operation ofeach motor 28 and stop the reexpansion preparatory to the supplementalhoning or sparking out. This mechanism includes the torque responsiveswitches 3S of the diiferent units: each of which switches is openedwhen the associated honing stones encounter the bore wall and apredetermined torque builds up in the drive connection.

The time delay relay 11R common to all of the hones is adjusted to closeits switch 11R1 at a time shortly after the reexpansion of all four ofthe hones has been completed. At this time, all of the relays 6Rcontrolling the reexpansion will have been deenergized thus closingswitches 6K2, 6R2n, b, and c in series with the switch 11R1 thuscompleting a circuit for activating a timer which, after a predeterminedinterval selected by adjustment of a knob 86, closes a switch 87. Duringthis interval, the four hones, all of which are expanded into lightcontact with the walls of their respective bores, will be reciprocatedback and forth and rotated to effect the supplemental honing of thesewalls.

After the expiration of the interval selected for supplemental honing,the switch 87 is closed. to complete 7 a circuit for energizing a relay12R thus closing a switch 12R1 which holds the relay energized and alsoa switch 12R2. The latter operates in conjunction with the switch S tocomplete a circuit for a relay 13R whose energization closes a switch13R1 to energize the solenoid 65 which, as above described, shifts thevalve 62 and initiates the inal upward movement of `the hones from thework bores. The relay 13R also closes a switch 13R2 in each unit which,through the then` closed switch 2S of that unit, reenergizes the relay9R to close the switch 82 and start the rapid motor 28. This collapsesthe hone until, after full collapse, the switch 2S of that hone isopened to deenergize the relay 9R and stop the motor 28.

In view of the energization of the solenoid 65 when the honing head 15now reaches the upper end of its normal working or honing stroke, thevalve 62 is held in the up-stroke position and the upward motion of thehead is continued until the dog 73 on the dial 68 reaches the positionshown in Fig. 2. At this point, the switch 4S is opened to interrupt thesealing circuits Vfor all of the then energized relays, the cycle beingterminated with the parts conditioned and positioned as shown in Figs.2, 3, and 4.

lt will be observed that the supplemental honing action by the differenttools and under light pressure is elected through the use of the sameactuators and controls that govern the primary honing, and this in spiteof the fact that the primary honing operations by the different tools iscompleted at different times. A minimum of additional equipment isrequired by adapting the control for the simultaneous performance of thesupplemental honing operations by the different tools, these operationsbeing timed by the single unit 85.

During the supplemental honing which extends over several reciprocationsof the tool head, plugs 51 of the dierent sizing devices will enter thework bores at the end of each down stroke. However, in the nextupstroke, the stones, although under light pressure, will remove anymark that may have been left near the bore due to entry of the sizingplug. Any substantial or noticeable marring of the finished surface bythe repeated engagement with the sizing plug during the sparking out isthus effectually avoided by the improved control.

Reference above to the collapse of the hone contemplates a release ofthe expanding pressure on the stones even though the latter may not movesubstantially away from the bore wall.

I claim as my invention:

l. A machine for honing a plurality of parallel bores in a workpiecehaving, in combination, a head reciprocable parallel to the axes of saidbores, a plurality of ex* pansible and contractible rotary honing toolson said head for operating simultaneously on said bores, individualpower actuators selectively operable to expand and contract therespective honing tools, means for advancing said head to enter saidtools into said bores and then to reciprocate the head and tools backand forth during rotation thereof, means for energizing said actuatorsto expand the respective tools into engagement with the bore walls,individual sizing devices associated with the respective tools and cachoperable to sense the attainment of a predetermined size of theassociated work bore during honing thereof and then control therespective actuators to collapse each of the tools successively as thebores come up to size, mechanism responsive to the attainment of saidpredetermined size of the last of said bores and operable to againreexpand all of said tools against the bore walls to restore the honingof all of the bores simultaneously in the continued reciprocation ofsaid head, and means operable after a measured amount of suchsupplemental honing of all of said bores to control said actuators andcollapse all of said tools whereby to interrupt the honing action. t 2.A machine for honing atleast two parallel bores in workpiece having, incombination, a head reciprocable parallel to the axes of said bores,expansible and contractible rotary honing tools on said head foroperating simultaneously on said bores, individual reversible poweractuators selectively operable to expand and contract the respectivehoning tools, means for advancing said head to enter said tools intosaid bores and then to reciprocate the head and tools back and forthduring rotation thereof, means for energizing said actuators to expandthe respec tive tools and maintain the stones thereof pressed againstthe bore walls, individual sizing devices associated with the respectivetools and each operable to sense the attainment of a predetermined sizeof the associated work borek during honing thereof, means controlled bythe sizing devices of the first of said tools to complete its bore toenergize the associated actuator and relieve the expanding pressure onthe hone, the second tool continuing to hone its bore, mechanismresponsive to the detection of proper size of the second bore to relievethe expanding pressure against the bore wall and expand both of saidtools against the bore walls to continue the honing of all of the boressimultaneously, and means operable after a measured amount of saidsimultaneous honing of all of said bores to control said actuators andcollapse all of said tools.

3. A machine for honing a plurality of parallel bores in a workpiecehaving, in combination, a head reciprocable parallel to the axes of saidbores, a plurality of expansible and contractible rotary honing tools onsaid head for operating simultaneously on said bores, individual poweractuators selectively operable to expand and contract the respectivehoning tools, mechanism for actuating said head and controlling saidactuators to advance said tools into the bores, expand the tools againstthe bore walls under heavy pressure and reciprocate the expanded toolsto produce primary honing of the bores, devices individually operable toterminate the primary honing by each tool as its bore cornes up to size,means operable automatically as an incident to completion of the primaryhoning by the last tool lto iinish its bore to initiate collapse of suchtool and to cause reexpansion of all of the tools against the bore wallsbut under reduced pressure whereby to effect supplemental honing of allof the bores simultaneously in the continued reciprocation of said headand rotation of the tools, timing means activated as an incident to saidreexpansion of said tools, and means operable after the lapse of aninterval measured by said timing means to terminate the supplementalhoning by all of the tools.

4. A machine for honing a plurality of parallel bores in a workpiecehaving, in combination, a head reciprocable along a path parallel to theaxes of said bores, a plurality of expansible and contractible rotaryhoning tools on said head for simultaneously honing said bores,individual power actuators selectively operable to expand and contractthe respective honing tools, mechanism for actuating said head andcontrolling said actuators to advance said tools into the bores, expandthe tools against the bore walls under heavy pressure and reciprocatethe expanded tools to produce primary honing of the bores, devicesindividually operable to terminate the primary honing by each tool asits bore comes up to size, means operable automatically as an incidentto completion of the primary honing of the last bore to be finished tocause reexpansion of all of said tools against the bore walls but underreduced pressure whereby to eiect supplemental honing of all of thebores simultaneously, a timer common to all of said tools activated asan incident to said reexpansion of said tools, and means operable afterthe lapse of an interval measured by said timer to terminate thesupplemental honing by all of the tools.

5. A machine for honing at least two parallel bores in a workpiecehaving, in combination, a head reciprocable parallel to the axes of saidbores, expansible and contractible rotary honing tools on Said head foroperating simultaneously on said bores, individual reversible poweractuators selectively operable to expand and contract the respectivehoning tools, means for advancing said head to enter said tools intosaid bores and then to reciprocate the head and tools back and forthduring rotation thereof, means for energizing said actuators to expandthe respective tools and maintain the stones thereof pressed against thebore walls, individual sizing devices associated with the respectivetools and each operable to sense the attainment of a predetermined sizeof the associated work bore during honing thereof, means controlled bythe sizing devices of the rst of said tools to complete its bore toenergize the associated actuator and relieve the expanding pressure onthe hone, the second tool continuing to hone its bore, mechanismresponsive to the detection to proper size of the second bore to relievethe eX- panding pressure against the bore wall and expand both of saidtools against the bore Walls to continue the honing of all of the boressimultaneously, means controlling said actuators and operable to preventreexpansion of either of said tools until after at least partialcollapse thereof, and means operable after a measured amount of saidsimultaneous honing of all of said bores to control said actuators andcollapse all of said tools.

References Cited in the file of this patent UNITED STATES PATENTS2,284,325 Kline May 26, 1942 2,318,830 Crompton May 11, 1943 2,356,223Crompton Aug. 22, 1944

